Has Big Bang inflation finally been verified?

March 27, 2014

Recently there has been plenty of excitement in the news about the recent Background Imaging of Cosmic Extragalactic Polarization (BICEP2) data. BICEP2 was studying the polarization (which is just the specific direction that light is pointing in, if it is pointing in many directions it is called un-polarized) of the cosmic microwave background radiation or CMB.

The CMB is basically a remnant of the Big Bang. It is the oldest light that we can see in the universe and thus can teach us about the nature of the early universe. Because of this the CMB has been a popular subject of study for Cosmologists.

What the BICEP2 discovered about the polarization is that the signal coming from the CMB is strong enough (specifically the value of r in cosmological terms, which was measured to be 0.2, much larger than the expected value for a non-inflationary universe) that it nearly rules out a non-inflationary universe, the key word being nearly.

Perhaps a slight digression into a short explanation of inflationary theory would be helpful. Inflation was first posited by Alan Guth in the early 1980s as a way to fix some of the troubling problems Big Bang theory was suffering from. Big Bang theory had won out over the steady -state theory of the universe, largely thanks to the measurements of the expansion of the universe by Hubble. The steady-state theory held the universe fixed, thus there could be no expansion of the universe in this model.

Though Big Bang theory had won out it was not without its problems. For instance the Big Bang model could not explain why the universe looks the same temperature in every direction. Why is the universe so smooth when some parts of the universe appear to have never been in contact with one another? Smoothing could have occurred if distant parts of the universe had been in thermal contact with one another, but the Big Bang model did not allow for this.

Another problem the Big Bang model faced was why is the universe flat? The Big Bang theory gave no answer to this question, though the universe interestingly needs to be flat to produce what we see around us today.

Another problem with the Big Bang model was that it could not explain why we do not see magnetic monopoles today, even though they were predicted to be found in large numbers by several theories (it should be noted however that many scientists do not believe magnetic monopoles even exist so this may not be a problem for the Big Bang model after all). Guth was really trying to understand the lack of magnetic monopoles and out popped the idea of inflation.

Inflation solves all of the above stated problems with the Big Bang. According to theory, there was a brief period of time after the Big Bang when the universe went through an extremely fast expansion. This fast expansion would have taken parts of the universe that were in thermal contact and very quickly moved them far away, thus explaining the smoothness of the universe. Inflation also forces the universe to become roughly flat. Finally, inflation would have briefly cooled the universe, greatly reducing the hypothetical production of magnetic monopoles and distributing the ones that were created so far apart that they would be extremely difficult to observe.

Until now Inflation has been little more than a hypothesis. Recently some observations have suggested that Inflation occurred but none so strong as BICEP2. This has raised a lot of excitement in the media, however the champagne bottles needn't be uncorked yet. A paper has just come out in the wake of the release of the BICEP2 data, and the paper has shown that the BICEP2 data is not a smoking gun yet. The data does not quite rule out other options. In fact, the data could still be completely explained without inflation at all.

However the data has pushed cosmology right up to the doorstep of Inflation. With improvement on other experimental results, Inflation could be proven once and for all very soon thanks to BICEP2. Or as often happens in science, we could be thrown a curveball and Inflation could be proven wrong, at least in its current form. In either case it shouldn't be long before we know for sure. It certainly gives us something exciting to look forward to.

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Jeremie is a Wilmington resident and Clarkson University graduate student. He can be contacted at adkscienceguy@yahoo.com